1. Field of the Invention
The present invention relates to a diagnostic method and apparatus for the detection of cancer in a living patient.
2. Prior Art
Attempts utilize the technique of nuclear magnetic resonance (NMR) to aid in arriving at a clinical diagnosis of cancer are well known in the prior art.
Damadian was the first to propose any medical use for nuclear magnetic resonance (NMR) and that was for the detection of malignancy. See R. Damadian, "Tumor Detection by Nuclear Magnetic Resonance," Science 171:1151-1153 (1971). U.S. Pat. No. 3,789,832 issued to Damadian covering an apparatus and method for application of nuclear magnetic resonance to surgically removed specimens to measure T.sub.1 and T.sub.2 for proton relaxation times, which values compared against values for healthy tissue were taken as an indication of cancer. U.S. Pat. Nos. 4,411,270 and 4,354,499 issued to Damadian cover apparatus and method for cancer detection with NMR imaging and scanning of whole-body specimens.
A number of other investigators also reported that nuclear magnetic resonance relaxation times (T.sub.1) for water protons in organs of tumor-bearing animals have higher values than the corresponding T.sub.1 for water structure in organs of healthy animals. See Frey et al, J. Natl. Cancer Inst. 49, 903 (1972); Inch et al, J. Nat. Cancer Inst. 52, 353 (1974); Iijima et al, Physiol. Chem. and Physics 5, 431 (1973); and Hazlewood et al, J. Natl. Cancer Inst. 52, 1849 (1974).
Today, despite uncertainty regarding mechanistic details, it is well known that biophysical changes which occur in malignant cells often result in alterations of the proton NMR signal. See D. G. Taylor et al, "A Review of the Magnetic Resonance Response of Biological Tissue and Its Applicability to the Diagnosis of Cancer by NMR Radiology," Computed Tomography, 5:122-133 (1981). Such changes form the physical basis for detection of tumors by proton NMR imaging. See R. Zimmerman et al, "Cerebral NMR: Diagnostic Evaluation of Brain Tumors by Partial Saturation Technique with Resistive NMR," Nueroradiology 27:9-15 (1985) and K. Ohtomo, "Hepatic Tumors: Differentiation by Transverse Relaxation Time (T.sub.2) of Magnetic Resonance Imaging," Radiology 155:421-423 (1985). However, NMR imaging is not likely to be widely applied as a screening test for malignancy because of accessibility and economic factors.
Proton NMR studies on excised tumors, as well as on plasma and serum, from experimental animals and patients have often shown differences in the relaxation parameters T.sub.1, T.sub.2 and T.sub.2 * as a function of malignancy. Such findings have been reported by the following:
L. McLachlan, "Cancer-induced Decreases in Human Plasma Proton NMR Relaxation Rates," Phys. Med. Biol. 25:309-315 (1980); PA1 F. Smith et al, "Nuclear Magnetic Resonance Imaging of the Pancreas," Radiology 142:677-680 (1982); PA1 P. Beall et al, "The Systemic Effect of Elevated Tissue and Serum Relaxation Times for Water in Animals and Humans with Cancers," NMR Basic Principles and Progress, P. Diehl et al, Eds., 19:39-57 (1981); PA1 R. Floyd, "Time Course of Tissue Water Proton Spin-lattice Relaxation in Mice Developing Ascites Tumor," Cancer Res. 34:89-91 (1974); PA1 C. Hazelwood et al, "Relationship Between Hydration and Proton Nuclear Magnetic Resonance Relaxation Times in Tissues of Tumor Bearing and Nontumor Bearing Mice: Implications for Cancer Detection," J. Natl. Cancer Inst. 52:1849-1853 (1974); and PA1 R. Klimek et al, "A Discussion of Nuclear Magnetic Resonance (NMR) Relaxation Time of Tumors in Terms of Their Interpretation as Self-organizing Dissipative Structures, and of Their Study by NMR Zeugmatographic Imaging," Ginekol Pol. 52:493-502 (1981).
However, due to extensive overlap of groups and small differences between the means of groups, these methodologies are not clinically useful.
While most of the prior art mentioned above describes applications of NMR to analysis of tissue, it is also known to subject body fluids to such analysis. This is described, for example, by Beall et al., supra.
The foregoing prior art studies and methods, as well as all other prior art NMR methods for the detection of malignancy, rely on the observation of the composite NMR signal arising from all protons in the tissue or blood derived samples. This composite signal is dominated by the protons of water, obscuring the NMR signal from other proton-containing constituents of the sample. Indeed, the prior art believed that the apparent correlation between malignancy and observed changes in NMR parameters was due to "changes in water structure," quoting Frey et al., supra.
In other applications of proton NMR spectroscopy, it was known to suppress the signal from the solvent (such as water) in sample.
At present, a reliable and statistically unequivocal NMR method of diagnosing the presence of cancer in a living patient has not been developed.